High pressure hot water secondary pipe sizes

[colmo40]

I have just had a Megaflow installed and am about to run the secondary pipes around the house for hot and cold water. However I have heard two different versions of what size to run.

The first is that you run 22mm up to a manifold then split off with 15mm to the appliances, as this will give you maximum flow rate.

The second is that you run 15mm to the manifold as this will give you less water required to fill the system when you turn on the tap, so faster response time, but still with sufficient flow.

If I do the the first there will be more water stored in the pipework, which is wasted energy.

If I do the second will there be sufficient flow rate (the bath is the greatest load)?

Any thoughts/experience to share on this, please?

 

[stevetheplumber]

22 mm to bath 15 tees to each apliance usually i try to run to bath first and everyting else fed seperately from below bath a lot of the time if its short runs to basin and wc i would use 10mm easier as its to run in pedestals
i feel best practice with any plastic is a few joins below floor as posssible